docs: def extract_uhs(dstore, what):
      """
      Extracts uniform hazard spectra. Use it as /extract/uhs?kind=mean or
      /extract/uhs?kind=rlz-0, etc
      """
      info = get_info(dstore)
      if what == '':  # npz exports for QGIS
          sitecol = dstore['sitecol']
          mesh = get_mesh(sitecol, complete=False)
          dic = {}
          for stat, s in info['stats'].items():
              hmap = dstore['hmaps-stats'][:, s]
              dic[stat] = calc.make_uhs(hmap, info)
          yield from hazard_items(
              dic, mesh, investigation_time=info['investigation_time'])
          return
      params = parse(what, info)
      periods = []
      for m, imt in enumerate(info['imtls']):
          if imt == 'PGA' or imt.startswith('SA'):
              periods.append(m)
      if 'site_id' in params:
          sids = params['site_id']
      else:
          sids = ALL
      if params['rlzs']:
          dset = dstore['hmaps-rlzs']
          for k in params['k']:
              yield ('rlz-%03d' % k,
                     hdf5.extract(dset, sids, k, periods, ALL)[:, 0])
      else:
          dset = dstore['hmaps-stats']
          stats = list(info['stats'])
          for k in params['k']:
              yield stats[k], hdf5.extract(dset, sids, k, periods, ALL)[:, 0]
      yield from params.items()